The problems concerning the control of constrained motion of manipulation robots are discussed in the paper. Two general problems of hybrid position/force control are considered: the problem of interaction between position and force control and the problem of contact between a robot and an environment. Some promising solutions to these problems are identified. It is shown that adaptive control is necessary to solve these problems. A new control scheme is proposed and results of computer simulations are presented

We present a method for kinematic calibration of open chain mechanisms based on the product of exponentials (POE) formula. The POE formula represents the forward kinematics of an open chain as a product of matrix exponentials, and is based on a modern geometric interpretation of classical screw theory. Unlike the kinematic representations based on the Denavit- Hartenberg (D-H) parameters, the kinematic parameters in the POE formula vary smoothly with changes in the joint axes, ad hoc methods designed to address the inherent singularities in the D-H parameters are therefore unnecessary. Another important advantage is that simple closed-form expressions can be obtained for the derivatives of the forward kinematic equations with respect to the kinematic parameters. After introducing the POE formula, we derive a least-squares kinematic calibration algorithm for general open chain mechanisms. Simulation results with a 6-axis open chain are presented.

In this paper an algorithm is proposed for the problem of path planning of redundant manipulators among obstacles by using a suitable formulation for robot configurations and path strategy. In particular robotic manipulators have been modelled by using reference points on the kinematic chain and their Cartesian coordinates description. The path planning has been formulated as an optimization problem for the determination of adjacent configurations and the path among obstacles with minimum manipulator displacement. The fully Cartesian coordinates description has been useful for the economy of the numerical procedure and for the constraints formulation of link interference and obstacles avoidance constraints. Some examples are reported which prove the practical feasibility of the path planning procedure, and the numerical results have been tested as applicable to industrial robots through easy programming because of the concept of adjacent configurations.

It is pleasant to realise that every leading institution and manufacturing company in the world is dealing with some aspects of flexible automation, because many researchers and managers in industry have found that the concept of designing and making goods and products on order, rather than for stock, is the key issue in order to cut down manufacturing costs and lead time, and eventually to stay in business in the future.

Nonlinear couplings between the various joints of a robotic arm cause trouble in robot control. One possibility to overcome these difficulties is offered by the concept of nonlinear decoupling. The latter leads to independent linear SISO systems, each of them describing the movement of one joint. Thus, an application of control concepts for linear SISO systems is possible. However, at present such decoupling controls are computed from the mathematical model of the arm, the so-called drive equations, whereas actuator dynamics are considered only in a secondary way. In this paper the decoupling problem for robots is investigated by accounting also for the actuator dynamics from the very beginning. This results in decoupling laws requiring a complete state feedback, i.e. not only joint positions and velocities but also the states of the various actuators have to be used. Further, formulas are given which make the computation of those states unsuitable for direct measurements.

In the problem of automatically controlling a wheeled vehicle so that a given reference point on the vehicle follows a prescribed path, several factors determine how the task can be accomplished; they are the shape of the path, the initial orientation angle, the steering angle limit and the position of the reference point on the vehicle. If the required steering angle exceeds the limit set by the steering mechanism or the required orientation angle is discontinuous at any point along the path, then the path cannot be followed. This paper investigates this motion feasibility problem, taking steering angle limit into consideration. First of all, we determine the dependence of the continuity of the orientation angle, steering angle and their derivatives on the continuity of the reference path and its derivatives, then discuss .the relationship between the steering angle limit and the feasible deviation angle intervals. Furthermore, we analyze in detail two typical motions, namely straight line motion and circular motion; some simulation results have been given based on a practical vehicle dimension.

In this paper we show that a robot manipulator with 6 degrees of freedom can be separated into two parts: arm with the first three joints for major positioning and wrist with the last three joints for major orienting. We propose 5 arms and 2 wrists as basic construction for commercially robot manipulators. This kind of simplification can lead to a general algorithm of inverse kinematics for the corresponding configuration of different combinations of arm and wrist. The approaches for numerical solution and closed form solution presented in this paper are very efficient and easy for calculating the inverse kinematics of robot manipulator.